The invention relates to a charging device including a charging unit and at least one interchangeable, rechargeable energy storage unit of a power tool.
The use of power tools with rechargeable, interchangeable energy storage units, in particular interchangeable batteries, for a wide variety of purposes has been known for a long time. In devices of this kind, the energy storage unit is as a rule plugged into a receptacle provided for this in a grip of the power tool; an energy supply to the power tool occurs via contact means provided for this purpose. One example of a power tool of this kind is the cordless drill disclosed in GB-A-2 420 031, in which a battery pack composed of a plurality of rechargeable cells is detachably connected to the grip. The battery pack has a contact means embodied in the form of a shaft provided with electrical contacts, which can be used to produce an electrical connection to an electrical circuit contained in the cordless drill or in a charging unit via corresponding electrical contacts of the cordless drill or charging unit. The contact means also enables a communication between the battery pack and the cordless drill or the charging unit. To this end, the battery pack is equipped with a microprocessor that stores certain operating parameters of the battery pack such as the charge state or the temperature measured by means of a sensor integrated into the battery pack and sends these parameters to the cordless drill or charging unit for further evaluation.